Arc welding



June 1954 R. w. TUTHILL ETAL 2,630,1 1

ARC WELDING Filed June 26, 195

A Fig.1.

GENERATOR w/n/ R/S/NG VOLT-AMPERE CHER/7C TEE/S Tl C u k t 0 I00 20a 30a 00 540 MPERES Inventors:

Roger- \MTuthill, Alanson U. We|ch,Jr.,

Patented June 1, 1954 UNITED STATES eAraNr OFFICE ARC WELDING Roger W. Tuthill, Fitchburg,

West Townsend, Electric Company, k

Welch, 31:, General New Yor and Alanson U. Mass, assignors to a corporation of Application June 26, 1952, Serial No. 295,612

12 Glaims.

Our invention relates to metal arc welding at current densities sufiiciently high to produce a self-regulating arc. More particularly our invention relates to this type of welding wherein to a spray of extremely fine droplets, which is projected from the end of the electrode in the direction in which the electrode is pointed.

To secure the desired high current densities in this type of welding, the electro e with normally used welding-current sources is usually less than a inch in diameter. Current densities of .093 inch in diameter. This high current density in the electrode wire results in a very rapid consumption thereof and consequently, the wire must be fed at a high rate of speed to match its consumption or burn-off rate in the arc. For example, when welding a A; inch aluminum plate with an aluminum electrode of .040 inch in diameter in an atmosphere of argon supplied at 63 tablish satisfactory operating conditions.

Consumption of the electrode in this type of arc welding is almost directly proportional to the current and is not very sensitive to the arc voltage. When a proper arc is established, it is automatically maintained by current supplied from the conventional direct current welder having a drooping volt-ampere characteristic. Usually, the electrode is connected to the positlve terminal of the generator and the work is connected to the negative terminal thereof. The inherent in this process of welding makes this process essentially automatic and eliminates controls for varying the speed of electrode feed in accordance with a characteristic of the are such as its With such used conself-regulation of the welding arc ventional generator having a drooping voltampere characteristic, the self-regulating character of the are results from a compensating change of its arc length for changes in electrode feed rate or changes in arc current for the same feed rate. As will be pointed out in greater detail below, this behavior of the are is due to its volt-ampere characteristics at diiierent arc gaps. These are characteristics have current than for a short arc.

We have determined that there is a critical arc length and voltage, or a narrow band thereof, below which welding by this process occurs with a great number of short circuits and above If weldpearance and good X-ray qualities. observation that the narrow band of critical voltage is from 1 to 2 volts in width.

Short circuits occurring below this critical operating voltage are the direct result of droplets from the arcing end of the electrode producing short circuits to the work and causing high currents to flow momentarily with a blasting effect resulting in spatter. The change in arc length, with generators heretofore used in this type of welding, may throw operation from the smooth spray type of arc to a rough fluctuating arc characterized by frequent intervals of short circuit causing excessive spatter along the weld. Also cause arc flashing to the welding tool with consequent destruction of the nozzle thereof. If the open circuit voltage of the conventional drooping volt-ampere characteristic generator is made less than twice the arc voltage, some improvement is obtained since greater changes in arc current are obtained for the same change in arc voltage. Still better results may be obtained with a generator having substantially the same voltage output regardless of load. However, in each case changes in electrode feed rate is productive of changes in arc length which may fall below the critical voltage and result in unsatisfactory welding conditions.

It is an object of our invention to provide a method or seli regulatin metal arc welding and apparatus therefor which provides for an adjustment of the welding on rent without producing a change in arc length by simply adjusting the speed of electrode teed.

It is also an object of our invention to pro- Vide a method and apparatus for this kind of welding in which the arc length adjustment may be made without a change in the welding current by simply changing the voltage adjusting means of the source of welding current.

Further objects of our invention will appear from the following description thereof.

W e accomplish these objects by supplying weldin current for the establishment of a self-regulating metal are from a generator or other source having a net rising volt-ampere characteristic of substantially the e form as the rising voltampere characteristic of the arc. When such are is at a length which is above the critical voltage, operation proceeds Without frequent short circuits due to molten particles bridging the physical gap between the electrode and the work. The more nearly the volt-ampere characteristic of the source, as evident at the terminals of the arc, corresponds to the volt-ampere characteristic of a self-regulating arc of a predetermined desired length, the more nearly will the are be held at this length during welding operations. With such a welding current source, welding cur rent can be adjusted by simply adjustin the speed of electrode feed. Furthermore, the length can be independently adjusted for given electrode size by simply adjusting the voltage of the source which will move its characteristic curve up and down relative to the various voltampere curves of arcs of different lengths for operation along a selected one of these curves. Segregation of the control into its functions of one control for arm length and one control for current and metal deposition rate, the latter bein only an adjustment of electrode feed speed. makes the welding operation very simple and practically foolproof. The arc length is no longer sensitive to variations of welding current or electrode feed speed when welding in accordance with our invention.

The features of our invention which we believe to be novel are set forth with particularity in the appended claims. The following more complete description of our invention may best be understood by reference to the accompanying drawing in which Fig. l is a more or less diagrammatic representation of apparatus in accordance with one embodiment thereof and Fig. 2 is a diagram or sketch showing the relationship of certain volt-ampere characteristics of the welding are for two different are lengths to a preferred volt-ampere characteristic of the generator employed in accordance with one embodiment of our invention. Fig. 2 also shows the relationship of the v0lt-ampere characteristics of generators heretofore employed relative to the volt ampere characteristics for the same two arcs of difierent lengths.

In Fig. l of the drawing we have illustrated apparatus suitable for performing shielded inert gas metal arc welding in accordance with one embodiment of our invention. This apparatus comprises a welding tool and a weldin generator having its output terminals connected to the work and to this tool for supplyin welding current to an arc established between the work and an electrode in the tool. The generator or this embodiment of particular design in that it has an output volt-ampere characteristic w ch .5

tangent or nearly tangent to the rising voltampere characteristic of the shielded inert gas metal welding arc. Satisfactory operation will be obtained in accordance with this embodiment or our invention if the volt-ampere characteristic of the generator, as evident at the electrode and the work, is of substantially the same form as the vclt-anipere characteristic of the welding arc. Ihe ideal condition is to have the machine ove1all-volt-ampe1"e curve coincident with the arc volt-ampere curve since with this operating condition the arc current can be forced from a very high Value to a very low value, or the reverse, by simply changing the electrode feeding speed without thereby producin any change in the arc length.

The weldin tool may be a machine tool which positions the arcing terminal of the electrode relative to the work and traverses it along a desired line of welding at a desired speed. More often, in this type of welding, it is a hand tool which may be manipulated by the welding operator. Such a hand tool is usually referred to as a Welding gun. In either case the welding tool provides means for directing the electrode through a nozale which supplies the shielding gas. Current is supplied to the electrode near its arcing terminal from one terminal or the welding generator and means are also provided for feedin the electrode at a substantially constant high rate of speed. When a hand tool or welding gun is employed, the current, gas, and electrode supply channels made flexible to permit easy manipulation of the gun during welding. In some instances, where the electrode feed rolls are embodied in the gun, they are connected by a flexible drive shaft with the feed rector which is located with the gas, current, and electrode supplies at a point remote from the gun.

The welding tool of Fig. l of the drawing is a representation of a hand tool more fully illustrated and described in an application for United States Letters Patent Serial No. 253,282, filed October 26, 1951, for Arc Welding Apparatus, in

the name of Alanson U. Welch, Jr., one of us,

and assigned to the same assignee as this invention.

The welding tool shown in Fig. 1 comprises an electrode guide formed by concentrically spaced tubes l and 2. A conduit 3 enters the upper end of tube l for supplying shielding gas thereto. The lower ends of tubes l and 2 terminate in an adapter i which closes the space between the inner and outer tubes and provides a continuation of the electrode and gas passageway in tube I. A socket in the lower end of the adapter 4 provides a support for a replaceable tip 5. The fusible metal electrode 5 is propelled by feed rolls 1 into and through tube i, adapter 4 and tip 5 in its passage through the tool toward the work 8. The adapter 4 and tip 5 are enclosed within a nozzle 9 which is supported on the lower end of a sleeve H) which frictionally engages and is supported by a resilient sleeve H which in turn frictionally engages and is supported by the lower end of tube 2 of the electrode guide. Tubes 1 and 2 of the electrode guide and two longitudinal partitions therebetwcen form supply and exhaust passageways for cooling fluid which is also circulated between sleeve H1 and sleeve ll through matching holes in the lower end of tube 2 and sleeve H. Welding current is supplied to electrode a through a brush 12 which is supported in the adapter 3 and spring-biased into engage- 5 ment with the electrode by spring ring I 3. The brush l2, adapter 4 and tubes 1 and 2 are formed Gas supplied to the inner tube I of the electrode guide passes through this tube to discharge passages is in the adapter t and into the upper end of the chamber formed by nozzle 9. This gas is discharged through the open end of nozzle 9 to form a shield about the arcing terminal of the electrode and the molten metal in the work 8 formed by the welding arc. As shown in Fig. 1, the work 8 is connected to the other terminal of the welding generator.

The electrode 6 is fed through the welding tool at a substantially constant high rate of speed by means of a feed motor 15. As illustrated, this motor is a direct current shunt motor having its input terminals connected to a suitable source of direct current it. The speed of this motor can be set or adjusted by adjusting a rheostat I l in circuit with its shunt field I 8. The armais mechanically connected feed rolls 1' of the welding propel electrode 6 through When welding with current conventional direct current drooping volt-ampere charof electrode feed is adjusted so that its fusion or hurn-off rate the arc will produce an arc of desired length. This also requires a concurrent adjustment of the welding generator to secure operation on that characteristic curve thereof which will supply the necessary fusing current at this desired operating voltage of the welding arc.

The conventional arc welding generator havtool which engage and the welding tool.

supplied from the generator having a acteristic the speed preaches zero at some finite current. justed to operate on a certain volt-ampere curve, the output of the generator is always on this curve. The generator may, however, be adjusted to operate on any one of a family of curves selected according to a selected adjustment of the welding generator. Assume operation on a char acteristic curve of this generator such that the Welding current and voltage results in a fusion or burn-oil rate of the electrode which matches its feeding rate and secures the desired deposit of electrode material through the arc. If, for any reason, the electrode feeding rate is increased over these equilibrium conditions, the welding operation will proceed along this generator characteristic to a point of increased current and reduced voltage. The increased current flow results in a faster burn-off of the electrode because its consumption is almost directly proportional to the arc current and is not very sensitive to are voltage. This increased burn-off rate due to increased current may match the increased feeding speed and if it does, a new stable condition will result. If, on the other hand, the electrode feeding speed were reduced below initial stable equilibrium conditions, the arc current would consume more electrode than was being supplied to the arc and consequently, the arc would get longer. Stability would then occur at a higher voltage where the current produced would just melt off the electrode at the new rate of supply to the arc. If, however, the wire feeding speed were held constant and the generator characteristic adjusted to give higher or lower current values, the are voltage would increase or decrease to new values productive of the same initial fusing current which matched burn-oil rate of the electrode with the constant rate of electrode feed. Sometimes, due to generator heating, and the resulting change to a lower output characteristic of the generator, the arc length may become so short that drops of molten metal will short circuit it causing spatter. Furthermore, the current may fall to such a low value, due to this heating effect, that with an initially satisfactory setting for a given electrode feeding rate, the generator is unable to produce enough current to match burn-oil rate against feeding rate of the electrode with the result that the electrode will plunge into the work and freeze.

Starting the arc in this type of welding can be accomplished by pulling a trigger of the welding gun to initiate feeding of the electrode and simultaneously to complete the electric circuit from the generator to the electrode and the work. Starting is not always easily accomplished, since the characteristic of the machine has a great deal to do with the ease of starting. If the welding characteristic of the machine is chosen where the volt-ampere characteristic is fairly steep, the short circuit current obtained is not large enough to initiate the arc and to establish molten fusing conditions on the end of the electrode quick enough to prevent the electrode from being forced into the metal in an unmolten state and freezing. It is essential consequently to choose a voltampere curve of such a value as to be able to produce considerable short circuit current compared to the current obtained during welding conditions.

It has been suggested that a substantially constant to the are from a direct current generator having a voltage equal to or slightly higher than the arc voltage. Such a generator will facilitate are starting but will produce changes in arc length in accordance with changes of current required to establish desired current flows or changes in feeding rate of the electrode. This follows as a direct resultof the volt-ampere characteristics of the welding arc. These characteristics have positive slopes which vary with arc length for a given size electrode, the characteristic for a long are being at a higher voltage for the same current than for a short arc.

In Fig. 2 of the drawing we have illustrated at 253 and 2| the volt-ampere characteristics for 4 inch and inch arcs established in an argon atmosphere between a inch diameter aluminum electrode and a plate of aluminum with the electrode at positive polarity. It will be noted that each of these curves has a positive slope and that the characteristic for the inch arc has a slope which is more positive than that for the inch are. We have also indicated in Fig. 2 at 22 a steep dashed curve marked Conventional Welder which is an approximation of the voltampere curve of an ordinary drooping characteristic direct current are welder. It will be seen that this intersects the inch arc curve at 25 volts for 280 amperes. It will also be evident that a slight change of arc current of from 280 to 305 amperes on this same machine curve would shorten the welding are from inch to inch, or wording this another way, if the electrode feeding device should speed up slightly it would halve the length of the welding are changing the arc amperes and burn-oil rate very slightly.

The difierence between the A2 and inch arc lengths is very substantial in this type of welding and may throw the operation from the smooth spray type of are operation to a rough fluctuating are characterized by frequent intervals of short circuit causing excessive spatter along the weld. Also, experience has shown that the operation of this process with a conventional welder is very critical. Unless the current and the wire feeding speed are very closely matched, the arc length is either so short as to force the operator to back the welding gun away to avoid stubbing or lengthens so rapidly as to cause arc-flashing to the gun with consequent destruction of the welding gun nozzle.

It will also be seen from the sketch of Fig. 2 that if we were to use a generator with output voltage constant, regardless of load, as shown by the characteristic curve '23, conditions would be substantially improved. For example, the arc current would have to increase from 280 to 400 amperes to obtain a change from the inch to the inch arc length. This large change of current would compensate for a fairly large change of wire feeding speed. However, this is not the ideal operation which is obtained in accordance with our invention by using a generator having a rising volt-ampere characteristic with increasing load. Preferably the arrangement should be such that the net voltage at the welding arc increases as volt-amperes increase, as shown by the dotted line 2% of Fig. 2. This line has been made nearly tangent to the arc volampere curve in order that it become distinguishable therefrom. However, for most eficctive operation the machine overall volt-ampere curve should be coincident with the arc voltage-ampere curve, since with this condition the arc current can be forced from very high value to a very low value, or the reverse, by changing the wire feeding speed without the are departing from the V inch arc length shown.

Any suitable source of welding current supplied having a volt-ampere characteristic which, as evident at the electrode and the work, is rising and within the range of an increase of at least 5 volts between no load and full load up to an increase of voltage and current of substantially the same magnitude the volt-ampere characteristic of the welding arc may be employed in practicing our invention. In Fig. l oi the drawing we have shown self-regulating generator which we have employed for this purpose. This welding generator 25 of the split pole type illustrated and described in U. S. Letters Patent lemme-even R. Bergman for Dynamo Electric Machine granted on May ll, 1920. It is to be understood, however, that the winding arrange-- ment and excitation is modified from that shown in the patent so as to obtain the desired rising voltampere characteristic.

The self-regulating generator 25 of Fig. l is of the .ype that has been used for battery charging. It has an open circuit voltage adjustable from 1i) to 35 volts. It may be adjusted. to provide 1.0 volts no load and 35 volts full load which is within the range of adjustment employed in practicing our invention. It may be adjusted, however, to provide 35 volts no load with volts full load in which case it has operating characteristics approximating those of the Bergman patent above referred to. It is of particular utilin the application we make of it in practicing our invention, since the field arrangement is such as to occasion very little field heating.

Consequently, the difierences between the hot and cold characteristics of the generator depend almost entirely on the differences between the cold and hot resistances of the output circuit including the armature conductors and the series field windings.

The physical structure and field winding arrangement of this self-regulating generator have been illustrated in the representation of this generator shown in Fig. 1. It comprises a field structure having main poles and 2?, cross poles 28 and 2s, and commutating poles 30 and 3|. Also it an armature structure whose conductors terminate in a commutator 32 engaged by main brushes 33 and 3d and an auxiliary brush 35 located between these main brushes. One main brush 33 is connected to the electrode 9 through a conductor 3% and the other main brush 3 is connected through the series field windings and a conductor 3? to the work 8. The welding conductors 36 and 3"! are of the usual type and for the lengths usually employed impose no more than a l to 5 volt resistance drop in the welding circuit. Consequently, the volt-ampere adjustment of the welding generator must be at the l to 5 volt higher value than that required by the volt-ampere characteristic of the welding are. From the explanation previously given, it is of course apparent that the volt-ampere characteristic of the welding generator must be such that, as evident at the electrode and work, it is rising and within the range exceeding 5 volts between no load and full load up to substantial coincidence with the volt-ampere characteristic of the are.

The main poles it and 2"! of the generator 25 re provided with shunt field windings 38 and 39 which are connected in series with one another across main brush 33 and auxiliary brush 35. These windings provide a saturating flux for the main field windings so that armature reaction produces very little if any change in the field strength through pole pieces 28 and 2'1. Cross pole pieces 23 and 29 are provided with shunt field windings ii] and M which are connected in series with one another to the sliding contacts of a pair of rheostats t2 and 13. These sliding contacts are operated in unison by a linkage 44 so that an adjustment of one rheostat requires a corresponding adjustment of the other rheostat. The rheostats l2 and 43 are connected across the main brush 33 and auxiliary crush 35 So that movement of the contacts thereof depending upon their positions will supply current in one direction or the other through the cross field shunt windings M3 and ll. The cross pole pieces 28 and 25) are provided with series windings 45 and 56, which are connected in series with one another and in series with the parallel connected series windings ill and ill of the commutating pole pieces 30 and 3i. The series field windings 45 and ifi for the cross pole pieces 28 and 29 are provided with taps so as to provide the diiierent operating volt-ampere characteristics required by the operating volt-ampere characteristics of welding arcs of different lengths. It will also be noted that cross pole pieces 28 and 29 have been illustrated as having larger dimensions than the main pole pieces 26 and 21. This is to provide for operation of the cross pole pieces at flux values less than saturation.

In Fig. 2, the characteristics of the arc and of the generator or source of supply have, for convenience, been illustrated as straight lines. This will follow as a natural consequence of the fact that the arc plasma will act as a pure resistance in the operating range. Ordinarily, however, the generator characteristic will not be a straight line and for preferred operation, it will usually be possible to secure coincidence or near coincidence of the arc and generator characteristics only within a given range of operating current values. Consequently, the adjustment or" the generator should be such that its characteristic and the are characteristic are tangent to one of the operating range of Fig. 2, where they intersect at an angle of about degrees. When they do so intersect at a sharp angle, it is, of course, apparent that when the operating current deviates from the initially set value there will be some slight change in the operating length of the welding are. This change, however, is quite small and is of minor consideration when compared with the voltage change that results when using a conventional generator having a decidedly drooping characthat occurs when using welder having a decidedly drooping volt-ampere characteristic.

From what has been stated above it is quite apparent that when the rising characteristic accordance with our in constant arc length. With this arrangement the welding current can be adjusted by simply adiusting the speed of the electrode feed. The arc length can be independently adjusted for a given electrode size by simply changing the voltage adjusting rheostat of the generator, which will move its characteristic curve up and down to coincide with the various arc volt-ampere curves. Segregation of the control into its functions of one control for arc length and one control for current and metal deposition rate, the latter being only the adjustment of electrode feed speed, makes the operation very simple and practically foolproof. By employing the preferred embodiment of our invention the arc length is no longer sensitive to variations in welding current or wire feed speed as in arrangements heretofore proposed.

The sketch of Fig. 2 of the drawing shows the static or equilibrium volt-ampere characteristics of the power source. It might seem that the rising output curve of the generator employed in accordance with our invention would cause instability. However, our tests have indicated that this is not the case. We believe that the reason for this is that the dynamic characteristics of the generator are different from the static characteristics illustrated. These dynamic characteristics of the generator will become evident by considering an example thereof. If while welding at 280 amperes, 25 volts, inch wire and a inch arc length, as shown in Fig. 2 of the drawing, the electrode feed were suddenly increased by turning the control knob, the first effect would be a momentary shortening of the welding are. This would result in a momentary lower arc voltage and a substantial increase in current because for the first short time interval the internal generated voltage of the generator would not change. This increased current would drop the voltage at the welding are because of the higher IR drop in the welding cables and generator armature. A fraction of a second later the effect of the series field windings in the generator would begin to appear in the generation of an increased voltage and the system would readjust itself to match the volt-ampere characteristic of the are simultaneously as the arc length increased back to the inch value. A like analysis can be made of the action resulting from suddenly decreasing the electrode feed speed.

Ehe particular volt-ampere arc characteristics above considered are believed to be the direct result of the presence of metallic vapor in the arc. There appears to be very little difference in the effect of steel and aluminum vapor and although the characteristic are curves of Fig. 2 are for an aluminum are, these same curves can e taken as characteristic for any other metal are. In determining these characteristics, however, it may be necessary to make some allowance for the voltage drop in electrodes having a high such as electrodes of stainless apparent that with different atthe arc the rising characteristic arc in a helium atmosphere, the curve is at a higher voltage characteristic of the higher voltage of an arc in helium. The characteristic of the arc will also change with the size of electrode employed. Thus, for a 1%; inch aluminum arc in argon the voltage values will be higher for the same are gap and current values.

In direct current welding, either straight or reverse polarity may be used in practicing our invention. With straight polarity in argon for example, it is possible to obtain higher rates of metal deposition for the same welding current amperage than with reverse polarity. However, when the electrode is negative it is often necessary to operate at higher current densities than desired for the type of welding being performed. It has been found that welding may be obtained at lower current densities with straight polarity by adding a small amount of oxygen to the argon. The addition of oxygen to argon has little effect on the rate of metal transfer when welding with reverse polarity, electrode positive. For certain kinds of welding there is also an upper limit of current values that may be used when ide folds form at the higher Although for most welding we believe that best results are obtained with an are long enough to avoid frequent intervals of short circuit, we do not intend to be limited to such operation in practicing our invention. Whether or not short circuiting is a factor, it is still desirable to be able to maintain arc length steadily, which the rising volt-ampere characteristic generator of our invention accomplishes.

While we have particularly described our invention as applied to shielded inert gas metal arc welding where it is expected to find its greatest utility, it is to be understood that it may be applied to any form of metal arc welding wherein the arc has the same self-regulating or selfcompensatory action. For example, it is applicable to welding in air, although as expected,

current values.

a dirty or oxidized weld is obtained because of the absence of a shielding medium. Other shielding mediums beside inert gases may be employed. We do not preclude the use of solid or liquid shielding mediums, such, for example, as the granular fluxes heretofore used in submerged melt welding.

Thus, while we have with regard to shielded described our invention inert gas metal are welding, modifications and adaptations thereof will readily occur to those skilled in the art. It is consequently our intention to cover all changes and modifications of the example of our invention herein chosen for purposes of disclosure which do not constitute departures from the spirit and scope of our invention. We consider our invention to be broad in scope and it should not be limited in any sense except as defined by the following claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. The method of welding with a self-regulating metal are established between a fusible electrode and the work which comprises energizing the welding are from a source of supply having a rising volt-ampere characteristic within the range of a voltage increase of at least 5 volts between no load and full load up to an increase of voltage with current of substantially the same magnitude as in the rising volt-ampere characteristic of said. self-regulating are when operating at a predetermined arc gap within the desired welding cur rent range for a fusible electrode of predetermined size, establishing an are between the work and said fusible electrode and feeding said fusible electrode to the work at a substantially constant rate of speed in accordance with its consumption in the are for a predetermined welding current flow, and controlling the rate of metal deposition from said electrode during welding by adjusting the constant feeding rate of said electrode in order to adjust the welding current flow from said source of supply within said range of desired welding current.

2. ihe method of welding with a self-regulating metal are established between a fusible electrode and the work which comprises energizing the welding are from a source of supply having a rising volt-ampere characteristic of substantially the same slope as the rising volt-ampere characteristic of said selfregulating are when operating at a predetermined arc gap within the desired welding current range for a fusible electrode of predetermined size, establishing an arc between the work and said fusible electrode and feeding said fusible electrode to the work at a substantially constant rat-e of speed in accordance with its consumption in the arc for a predetermined welding current flow, and controlling the rate of metal deposition from said electrode during welding by adjusting the constant feeding rate of said electrode in order to adjust the welding current flow from said source of supply within said range of desired welding current.

3. The method of welding with a self-regulating metal are established between a fusible electrode and the work which comprises energizing the welding are from a source of supply having substantially the same rising volt-ampere charaoteristic as said self-regulating are when operating within the desired welding current range for said fusible electrode of predetermined size, adjusting the voltage of said source to establish between said fusible electrode and the work a predetermined arc gap, establishing an arc between the work and said electrode and feeding said fusible electrode to the work at a substantially constant rate of speed in accordance with its consumption in the are for a predetermined welding current flow, and controlling the rate of metal deposition from said electrode during welding by adjusting the constant feeding rate of said electrode in order to adjust the welding current flow from said source of supply within said range of desired welding current.

4. The method of shielded inert gas metal arc welding 'th at fusible electrode conducting welding current at densities sufficient to produce a spray type deposit through the are, said method comprising energizing the welding are from a source of supply having a rising volt-ampere characteristic within the range of a voltage increase of at least 5 volts between no load and full load up to an increase of voltage with current of substantially the same magnitude as in the ring volt-ampere characteristic of said selfregulating are when operating at a predetermined arc gap within the desired welding current range or a fusible electrode of predetermined size, stablishing an arc beti n the work and said usible ne ro-fie in a shiel..ing atmosphere of gas elected from the group of argon, helium and mixtures thereof, feeding said fusible electrode to the work at a substantially constant rate of speed in accordance with its consumption in the are for predetermined welding current flow, adjusting the voltage of said source to establish between said fusible electrode and the work a predetermined arc gap which will prevent droplets of molten metal discharged from the fusible end of said clecnede lrom short circuiting said gap when operating within said desired welding current range, and controlling the rate of metal deposition from said fusible electrode during welding by adjusting the constant feeding rate of electrode in order to adjust the welding current flow from said source of supply within said range of desired welding current.

5. The method of shielded inert gas metal arc welding with a self-regulating metal are established between the work and a fusible electrode conducting welding current at densities sufficient to produce a spray type deposit through the are, said method comprising energizing the welding are from a source of supply having substantially the same rising volt-ampere characteristic as said self-regulating are when operating within the desired welding current range for an electrode of predetermined size, adjusting the voltage of said source to establish between said fusible electrode and the work a predetermined arc gap which will prevent droplets of molten metal discharged from the fusible end of said electrode from short circuiting said gap when operating within said desired welding current range, establishing an are between the work and said fusible electrode in a shielding atmosphere of gas selected from the group of argon, helium and mixtures thereof, feeding said fusible electrode to the work at a substantially constant rate of speed in accordance with its consumption in the are for a predetermined welding current flow, and controlling the rate of metal deposition from said fusible electrode during welding by adjusting the constant feeding rate of said electrode in order to adjust the welding current flow from said source of supply within said range of desired welding current.

6. Apparatus for metal arc welding with a selfregulating are having a rising volt-ampere characteristic determined by its arc length, said apparatus comprising means for feeding an electrode at a substantially constant rate of speed, means for adjusting said substantially constant feeding rate of said last mentioned means, and means for supplying welding current to said electrode and the work at current densities in said electrode sufiiciently high to produce a selfregulating arc, said means having a volt-ampere characteristic which, as evident at the electrode and the work, is rising and within the range of an increase of at least volts between no load and full load up to an increase of voltage with current of substantially the same magnitude as in the volt-ampere characteristic of said welding are when operating at a predetermined arc length.

7. Apparatus for metal arc welding with a selfregulating arc having a rising volt-ampere characteristic determined by its arc length, said apparatus comprising means for feeding an electrode at a substantially constant rate of speed, means for adjusting said substantially constant feeding rate of said last mentioned means, means for supplying welding current to said electrode and the work at current densities in said electrode sufficiently high to produce a self-regulating arc, said means having a volt-ampere characteristic which, as evident at the electrode and the work, is rising and within the range of an increase of at least 5 volts between no load and full load up to an increase of voltage with current of substantially the same magnitude as in the volt-ampere characteristic of said welding arc when operating at a predetermined arc length, and means for adjusting the volt-ampere characteristic of said welding current supply means.

8. Apparatus for metal arc welding with a self-regulating arc having a rising volt-ampere characteristic determined by its length, said apparatus comprising means for feeding an electrode at a substantially constant rate of speed, means for adjusting said substantially constant feeding rate of said last mentioned means, and means for supplying welding current to said electrode and the work at current densities in said electrode sufliciently high to produce a self-regulating arc, said means having a volt-ampere characteristic which, as evident at the electrode and the work, is rising and for the desired welding current range of substantially the same slope as the volt-ampere characteristic of said welding arc when operating at a predetermined arc length.

9. Apparatus for metal arc welding with a selfregulating are having rising volt-ampere characteristics each of which is different for difierent arc lengths, said apparatus comprising means for feeding an electrode at a substantially constant rate of speed, means for adjusting said substantially constant feeding rate of said last mentioned means, means for supplying welding current to said electrode and the work at current densities in said electrode sufficiently high to produce a spray type of deposit from the arcing tip of said electrode, said means having a volt-ampere characteristic which, as evident at the electrode and the work, is rising and for the desired welding current range of substantially the same slope as the volt-ampere characteristic of said welding are when operating at a predetermined arc length, and means for adjusting the operating voltage of said welding current supply means.

10. Apparatus for metal arc welding with a self-regulating are having rising volt-ampere characteristics each of which is different for different arc lengths, said apparatus comprising means for feeding a fusible electrode at a substantially constant rate of speed, means for adjusting said substantially constant feedingrate of said last mentioned means, a direct current generator for supplying welding current to said electrode and the work, said generator having a volt-ampere characteristic which, as evident at the electrode and the work, is rising and of substantially the same slope as the volt-ampere characteristic of said welding arc when operating at a predetermined arc length, low resistance leadconnectin one terminal of said generator to s electrode and the other terminal of said generator to the work, and means for adjusting the operating voltage of said generator.

11. Apparatus for shielded inert gas metal arc welding with a fusible electrode conducting welding current at densities sufficient to produce a spray type deposit through the are, said apparatus comprising a source of weldingcurrent having substantially the same rising volt-ampere characteristic as said self-regulating are at different arc gaps and voltages when operating within the desired welding current range with electrodes of different sizes, means for adjust ing the voltage of said source for the same welding current range, means for establishing about the arcing terminal or" said arc and the molten portions of the work a shielding atmosphere of gas selected from the group of argon, helium and mixtures thereof, means for feeding said fusible electrode to the work at a substantially constant rate of speed in accordance with its consumption in the are for a predetermined electrode size and welding current, and means for adjusting the constant feeding rate of said electrode feeding means.

12. Apparatus for shielded inert gas metal arc welding with a self-regulating are having rising volt-ampere characteristics each of which is different for different arc lengths, said apparatus comprising means for feeding a fusible electrode at a substantially constant rate of speed, means for adjusting said substantially constant feeding rate of said last mentioned means, means for supplying about the arcing terminal of said electrode and the molten portions of the work, a shielding gas selected from the group consisting of argon, helium and mixtures thereof, a direct current enerator for supplying welding current to said electrode and the work, said generator having a volt-ampere characteristic which, as evident at the electrode and the work, is rising and of substantially the same slope as the volt- Number Name Date 1,340,004 Bergman May 11, 1920 1,483,612 Morton Feb. 12, 1924 2,332,950 'I'annheim Oct. 26, 1943 2,504,888 Muller et a1 Apr. 18, 1950 2,532,410 Kennedy Dec. 5, 1950 

